Keyed fibre optic connector

ABSTRACT

A keyed connector system for providing selective interconnection between a receptacle socket and a connector plug terminating an optic fibre, the connector plug adapted for insertion into the receptacle socket. The keying system comprises a raised boss configured to one of a plurality of predefined boss keying geometries and a cavity configured to one of a plurality of predefined cavity keying geometries. The boss is either in one of the receptacle socket or on a forward end of the connector plug and the cavity is formed in the other of the receptacle socket or the forward end of the connector plug. At least one of the predefined boss keying geometries matches at least one of the predefined cavity keying geometries. When the boss keying geometry matches the cavity keying geometry, the boss can be inserted into the cavity thereby interconnecting the connector plug with the receptacle socket.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims priority under 35U.S.C. §120 to, co-pending U.S. patent application Ser. No. 11/779,335entitled “Back-To-Back Receptacle” filed on Jul. 18, 2007, which is adivisional of, and claims priority to, U.S. application Ser. No.10/945,935 entitled “Keyed Fibre Optic Connector,” filed on Sep. 22,2004 and now U.S. Pat. No. 7,258,493, which claims priority under 35U.S.C. §119(e) to U.S. Provisional Application Ser. No. 60/504,189,entitled “Keyed Fibre Optic Connector,” filed on Sep. 22, 2003, each ofwhich is incorporated herein by reference in its entirety.

BACKGROUND

1. Field of Invention

The present invention relates to a keyed fibre optic connector. Inparticular, the present invention relates to an interlocking connectorand receptacle pair for fibre optic cables with a geometric keyingsystem moulded into the interface thereby preventing connectors with afirst key from being interconnected via a receptacle having a differingkey.

2. Discussion of Related Art

Optical fibres terminated by connectors and the receptacles which areadapted to received these connectors are an important part of virtuallyany fibre optic communications system. For example, such connectors andreceptacles may be used to interconnect fibre segments to create longerlengths, to connect optic fibre to active or passive devices, etc.However, in some cases, for example for security reasons or in order tobetter manage a telecommunications network, it is desired to physicallylimit the insertion of a connector plug into a particular receptaclesocket, and as a result prevent the transmission of data via thatconnector plug and receptacle socket.

The prior art reveals a variety of systems for preventing a connectorplug from being inserted into a receptacle socket. One of these priorart systems comprises at least one tab arranged at a certain position onthe connector plug, each of which is adapted for insertion into acorresponding tab receiving indentation moulded in the receptaclesocket. In the absence of such a hollow the tab buts against the openingof the receptacle socket, thereby preventing the connector plug frombeing completely inserted into the receptacle socket, thereby preventingthe connector plug from being correctly interconnected with thereceptacle socket. One drawback of these prior art designs is that thatthe tab, being typically moulded into the plastic connector plughousing, can be easily removed by filing or using a sharp blade or thelike. Another drawback is that such prior art designs only allow twotypes of connector plugs to be differentiated between: connector plugswith a tab and connector plugs without a tab.

The prior art also reveals keying systems such as the U.S. patentapplication Ser. No. published with the No. 2002/0126960 A1 comprising aconnector plug and receptacle socket. Interconnection of the connectorplug and receptacle socket is limited to connector plug/receptaclesocket pairs where a key within the receptacle socket mates with acorresponding key receiving slot in the connector plug. A connector plugwith a key receiving slot in one position is unable to interconnect withreceptacle sockets with a differently positioned key. As a result, byproviding a number of differently positioned keys and key receiving slota system of selective interconnection between connector plugs andreceptacle sockets can be arrived at. These systems, however, aregenerally impractical in many fibre optic systems given the relativelysmall size of the connector plug and the receptacle socket.

SUMMARY

In order to address the drawbacks of the prior art, there is provided akeying system for providing selective interconnection between areceptacle socket and a connector plug terminating an optic fibre, theconnector plug adapted for insertion into the receptacle socket. Thekeying system comprises a raised boss configured to one of a pluralityof predefined boss keying geometries and a cavity configured to one of aplurality of predefined cavity keying geometries. The boss is either inone of the receptacle socket or on a forward end of the connector plugand the cavity is formed in another of the receptacle socket or theforward end of the connector plug. At least one of the predefined bosskeying geometries matches at least one of the predefined cavity keyinggeometries. When the boss keying geometry matches the cavity keyinggeometry, the boss can be inserted into the cavity therebyinterconnecting the connector plug with the receptacle socket.

There is also provided a receptacle for providing selectiveinterconnection with a connector plug terminating a first optic fibre,the connector plug comprising a cavity having a connector keyinggeometry formed in a forward end thereof. The receptacle comprises atleast one receptacle socket comprising a raised boss therein, the bosshaving a shape corresponding to one of a plurality of predefinedreceptacle keying geometries, the connector keying geometrycorresponding to one of the predefined receptacle keying geometries.When the receptacle keying geometry corresponds to the connector keyinggeometry, the connector plug can be inserted into the receptacle socket.

Furthermore, there is provided a receptacle for providing selectiveinterconnection with a connector plug terminating a first optic fibre,the connector plug comprising a boss having a connector keying geometryformed in a forward end thereof. The receptacle comprises at least onereceptacle socket comprising a cavity formed therein, the cavity havinga shape corresponding to one of a plurality of predefined receptaclekeying geometries, the connector keying geometry corresponding to one ofthe predefined receptacle keying geometries. When the receptacle keyinggeometry corresponds to the connector keying geometry, the connectorplug can be inserted into the receptacle socket.

Additionally, there is provided a connector terminating an optic fibrefor providing selective interconnection with a receptacle socket, thereceptacle socket comprising a raised boss having a receptacle keyinggeometry formed therein. The connector comprises a connector plugadapted for insertion into the receptacle socket and comprising acavity, the cavity having one of a plurality of predefined connectorkeying geometries formed in a forward end thereof, the receptacle keyinggeometry corresponding to one of the predefined connector keyinggeometries. When the receptacle keying geometry corresponds to theconnector keying geometry, the connector plug can be inserted into thereceptacle socket.

Also there is provided a connector terminating an optic fibre forproviding selective interconnection with a receptacle socket, thereceptacle socket comprising a cavity having a receptacle keyinggeometry formed therein. The connector comprises a connector plugadapted for insertion into the receptacle socket and comprising a bosshaving one of a plurality of predefined connector keying geometriesformed in a forward end thereof, the receptacle keying geometrycorresponding to one of the predefined connector keying geometries. Whenthe receptacle keying geometry corresponds to the connector keyinggeometry, the connector plug can be inserted into the receptacle socket.

Furthermore, there is provided a system for providing selectiveinterconnection between first and second optic fibres. The systemcomprises a receptacle comprising back-to-back receptacle sockets, eachof the sockets comprising a raised boss disposed therein and configuredto one of a plurality of predefined receptacle keying geometries, afirst connector plug terminating the first optic fibre, the plug adaptedfor insertion into a first of the back-to-back receptacle sockets andcomprising a cavity formed in a forward end of the plug, the cavityconfigured to one of a plurality of predefined connector keyinggeometries, and a second connector plug terminating the second opticfibre, the plug adapted for insertion into a second of the back-to-backreceptacle sockets and comprising a cavity formed in a forward end ofthe plug, the cavity configured to one of a plurality of predefinedconnector keying geometries. At least one of the predefined connectorkeying geometries matches at least one of the predefined receptaclekeying geometries and when a receptacle keying geometry of a boss of afirst of the back-to-back receptacle sockets corresponds to theconnector keying geometry of the first cable and a receptacle keyinggeometry of a boss of a second of the back-to-back receptacle socketscorresponds to the connector keying geometry of the second cable, thefirst cable can be inserted in the first socket and the second cable canbe inserted in the second socket bringing the first optic fibre intoaxial alignment with the second optic fibre.

Additionally, there is provided a receptacle for providing selectiveinterconnection between first and second fibre optic cables, each cablecomprising a connector plug comprising a cavity having a connectorkeying geometry formed in a forward end thereof. The receptaclecomprises back-to-back receptacle sockets, each of the socketscomprising a raised boss, the boss having a shape corresponding to oneof a plurality of predefined receptacle keying geometries. Each of theconnector keying geometries corresponds to one of the predefinedreceptacle keying geometries and when the receptacle keying geometry ofthe boss of a first of the back-to-back receptacle sockets correspondsto the connector keying geometry of the first cable and when thereceptacle keying geometry of the boss of a second of the back-to-backreceptacle socket corresponds to the connector keying geometry of thesecond cable, the connector plug of the first cable can be inserted inthe first socket and the connector plug of the second cable can beinserted in the second socket, thereby interconnecting the first andsecond cables.

There is also provided a field-configurable receptacle for providingselective interconnection with a connector plug in a fibre opticcommunications system, the connector plug comprising a connector keyinggeometry formed in a forward end thereof. The receptacle comprises atleast one receptacle socket adapted for receiving the connector plug andcomprising a configurable shape, the shape corresponding to one of aplurality of predefined receptacle keying geometries. The he connectorkeying geometry corresponds to one of the predefined receptacle keyinggeometries and when the shape is configured to correspond to theconnector keying geometry, the connector plug may be inserted into thesocket.

In addition, there is provided a field-configurable connector forproviding selective interconnection with a receptacle in a fibre opticcommunications system, the receptacle comprising at least one receptaclesocket having a receptacle keying geometry formed therein. The connectorcomprises a connector plug adapted for insertion into the receptaclesocket and comprising a configurable shape corresponding to one of aplurality of predefined connector keying geometries. One of thepredefined connector keying geometries corresponds to the receptaclekeying geometry and when the receptacle keying geometry corresponds tothe connector keying geometry, the connector plug can be inserted intothe receptacle socket.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an orthogonal view of a connector in accordance with anillustrative embodiment of the present invention;

FIG. 2 is a front plan view of a connector in accordance with anillustrative embodiment of the present invention;

FIG. 3 is an orthogonal view of a receptacle in accordance with anillustrative embodiment of the present invention;

FIG. 4 is a front plan view of a receptacle in accordance with anillustrative embodiment of the present invention;

FIG. 5A is an orthogonal view of a connector in accordance with analternative illustrative embodiment of the present invention;

FIG. 5B is a side plan view of a connector in accordance with analternative illustrative embodiment of the present invention;

FIG. 6 is a front plan view of a receptacle with a connector installedin a socket thereof in accordance with an illustrative embodiment of thepresent invention;

FIG. 7 is a side cut away view along VII-VII in FIG. 6;

FIG. 8 is an orthogonal view of a connector in accordance with analternative illustrative embodiment of the present invention;

FIG. 9 is a front plan view of a receptacle in accordance with analternative illustrative embodiment of the present invention;

FIG. 10 is an orthogonal view of a connector in accordance with a secondalternative illustrative embodiment of the present invention;

FIG. 11 is an orthogonal view of a receptacle in accordance with ansecond alternative illustrative embodiment of the present invention;

FIG. 12 is an orthogonal view of a receptacle in accordance with analternative illustrative embodiment of the present invention;

FIG. 13 is an orthogonal view of a connector in accordance with a thirdalternative illustrative embodiment of the present invention;

FIG. 14 is an orthogonal view of a connector in accordance with a forthalternative illustrative embodiment of the present invention;

FIG. 15 is an orthogonal view of a receptacle in accordance with a forthalternative illustrative embodiment of the present invention;

FIG. 16 is an orthogonal view of a receptacle in accordance with a fifthalternative illustrative embodiment of the present invention;

FIG. 17 is a front plan view of a receptacle in accordance with a fifthalternative illustrative embodiment of the present invention;

FIG. 18 is a side cut away view along VIII-VIII in FIG. 17 of areceptacle in accordance with a fifth alternative illustrativeembodiment of the present invention;

FIG. 19A is an orthogonal view of an illustrative embodiment of aninstaller modifiable connector keying system;

FIG. 19B is a front orthogonal view of a second illustrative embodimentof an installer modifiable connector keying system; and

FIG. 20 is a front orthogonal view of a receptacle for mounting onactive devices in accordance with an illustrative embodiment of thepresent invention.

DETAILED DESCRIPTION

Referring now to FIG. 1, a fibre optic connector in accordance with anillustrative embodiment of the present invention will be described. Theconnector, generally referred to using the reference numeral 2, whichserves to connect a fibre optic cable 4 to a receptacle (not shown) isdisclosed. As illustrated, connector 2 forms part of a cable assemblywith an LC type connector plug attached at one end. It should be notedthat although the illustrative embodiment of the present invention isdescribed in reference to LC type connectors, it is not intended tolimit the invention to this type of connector. Accordingly, the presentinvention may also be used, for example, with LC, SC, FC, MU and othersimilar connectors having a ferrule guide and/or support.

Still referring to FIG. 1, the connector is comprised of a connectorplug housing 6, fabricated from a suitable non-conductive material suchas glass filled thermoplastic, through which the optic fibre 8 extendsprotruding from a forward end 10 thereof. The optic fibre 8 is heldrigidly within a hollow ferrule 12, fabricated from a suitable stiffnon-conductive material such as ceramics, which is in turn held in axialalignment within the plug housing 6, thus ensuring that the opticalfibre is maintained in substantially axial alignment with the centralaxis A of the plug housing 6. Typically, ferrule 12 is held rigidlyinside the plug housing 6, but may also be spring loaded allowing somemovement of the ferrule 12, and thus the optic fibre 8, forward andbackwards along the central axis A.

A cavity 14, also in axial alignment with the central axis A, is mouldedor machined into the forward end 10 of the plug housing 6 with the opticfibre 8/ferrule assembly 12 being axially aligned therein. A flexiblelocking tab or latch 16 is attached to the outside of the plug housing 6allowing the plug housing 6 to be removeably attached to a suitablereceptacle (not shown). The join between optic fibre cable 4 and theplug housing 6 is protected by means of a flexible strain-relieving boot18, typically manufactured from rubber, rubberised plastic or the like.A pair of raised tabs as in 20 may be moulded to the outside of the plughousing which, as will be seen below, mate with correspondingindentations in the receptacle (both not shown).

During fabrication, the optic fibre 8 is typically inserted through theferrule 12 and bonded thereto with an appropriate adhesive or bondingtechnique. The ends of the optic fibre 8/ferrule 12 are then cut andpolished according to a predefined geometry dictated to the standardbeing implemented. The polishing results in an exposed end 22 of theoptic fibre 8 extending forward of the forward end 10 of the plughousing, thereby allowing light to propagate to and from the optic fibre8.

Referring now to FIG. 2, a first illustrative embodiment of a keyingsystem in accordance with the present invention will be described inmore detail. The cavity 14, through which the optic fibre 8/ferrule 12assembly extends, is configured to one of a plurality of predefinedconnector keying geometries. The connector keying geometry isillustratively provided by a cavity having a cavity keying geometryhaving an oval or egg shaped cross section with a first generallycircular concentric portion of radius X₁ and a keying portion 24extending a distance of X₂ from the centre of the optic fibre 8, with X₂being illustratively greater than radius X₁. As illustrated in FIG. 2,the cavity keying portion 24, for example a flute, notch orprotuberance, is illustratively symmetric about an axis B, with axis Bat a predetermined connector keying angle θ from the horizontal plane C.Of course, the maximum point of extension X₂ from the core of the opticfibre 8 must be chosen such that it is sufficiently less than distance ybetween the centre of the optic fibre 8 and the outer surface of theplug housing 6 to ensure that sufficient material remains between thecavity 14 and the outer surface of the plug housing 6 for all keyingangles θ. The other dimensions of the cavity keying portion 24 such asthe width and profile, are preferably selected such that the cavitykeying portion 24 is difficult to modify, for example by removing thecavity keying portion 24 using a knife or the like in the case of aprotuberance, or to modify without destroying the connector 2, therebydeterring the user from modifying the connector 2 for other purposes.

The cross section of the cavity keying portion 24 could alternatively beof a different shape, for example a square notch or concave depressionin the side wall of the cavity 14, or could also be asymmetric. As willbe seen below, the combination of the cavity keying portion 24 with theconnector keying angle θ provides one embodiment for the connectorportion of the keying system.

Referring now to FIG. 3, a receptacle in accordance with an illustrativeembodiment of the present invention will be described. The receptacle,generally referenced using the numeral 26, illustratively comprises areceptacle housing 28 fabricated from a non-conductive material such asglass filled thermoplastic into which are moulded one or more receptaclesockets 30. Referring to FIG. 1 in addition to FIG. 3, the sockets 30are dimensioned for receiving the forward end 10 of the plug housing 6which is held snugly therein. Note that, although in the presentillustrative embodiment a receptacle 26 having a duplex configurationwith two (2) sockets 30 is disclosed, the receptacle 26 could also besimplex with a single socket 30, or provide for three (3) or moresockets 30.

Referring back to FIG. 3, the receptacle housing 28 can be fastened to apatch bay panel or the like (not shown) by means of a pair of integratedflanges 32 and/or by screws or similar fasteners inserted through thecut outs 34 in the flanges.

Each receptacle socket 30 is terminated by a rear wall 36 and onto whichis moulded a raised boss 38, illustratively of an oval or egg shape,having a circular ferrule accepting bore 40 therein. Also moulded intothe socket 30 is a reciprocal locking mechanism 42 which, referring toFIG. 1 in addition to FIG. 3, mates with the latch 16, thereby securelyinterlocking the connector 2 with the receptacle 26 when the connectorplug housing 6 is completely inserted into the socket 30. A pair ofindentations 44 are also moulded in the socket 30 which mate with thecorresponding tabs 20 moulded into the connector plug housing 6. Thetabs 20 prevent a connector 2 from being completely inserted into areceptacle 26 which does not have these indentations. Note that in analternative embodiment both the tabs 20 and indentations 44 could beabsent without otherwise affecting the present invention.

Referring now to FIG. 4, each socket 30 is configured to one of aplurality of predefined receptacle keying geometries. Illustratively,the receptacle keying geometry is provided by a raised boss 38 having aboss keying geometry, mounted on the rear wall 36 of the socket 30comprising an oval or egg shaped cross section having a first generallycircular concentric portion of radius x₁ and a keying portion 46, forexample a protuberance such as a ridge, projecting a distance of x₂ fromthe centre of the ferrule cavity 40, x₂ being illustratively greaterthan radius x₁, although in a given implementation the distance of x₂could also be smaller than x₁. The boss keying portion 46 isillustratively symmetric about an axis such as D, with axis D at apredetermined receptacle keying angle φ₁ from the horizontal plane E.

Referring to FIG. 2 in addition to FIG. 4, in order for a connector 2 tocorrectly mate with a receptacle 26, the keying angles θ and φ as wellas the lengths X₁, X₂ and x₁, x₂ must match such that the cross sectionof the raised boss 38 is the mirror image of the cross section of thecavity 14 and that the cavity 14 fits snugly over the raised boss 38.For example, in the illustrative embodiment if the keying angles θ and φdo not match, then a portion of the front surface 10 of the connectorplug housing 6 will butt against the boss keying portion 46 of theraised boss 38 thereby preventing the connector 2 from being correctlyinserted into the receptacle 26.

It is foreseen that a combination of eight (8) keying angles θ and φequally distributed around 360° (for example 0°, 45°, 90°, 135°, 180°,225°, 270°, 315°.) will provide adequate keying for most applications,although it will be understood that this could easily be extended tosixteen (16) or even greater with precision manufacturing of theconnector 2 and receptacle 26. Referring back to FIG. 4, it is alsoforeseen that receptacles 26 can have multiple sockets 30 ₁, 30 ₂, 30 ₃each socket 30 ₁, 30 ₂, 30 ₃ having a raised boss 38 ₁, 38 ₂, 38 ₃ withdiffering keying angles φ₁, φ₂, φ₃. It will be understood that althougha receptacle 26 is shown with three raised bosses 38 ₁, 38 ₂, 38 ₃, andthree keying angles φ₁, φ₂, φ₃ a receptacle 26 could easily bemanufactured having many sockets 30, each socket 30 having acorresponding raised boss 38 and keying angle φ in any one of a numberof combinations. It should also be understood that multiple connectors 2with different connector keying angles θ can also be bundled togetherinto a multiple connector assembly (not shown). It should also beunderstood that sockets such as 30 ₄ may be included with raised bossessuch as 38 ₄ which are circular in cross section without the inclusionof a receptacle keying portion, thereby allowing conventional non-keyedconnectors to be inserted into the receptacle 26.

Note that, although the above illustrative embodiment has been describedwith the cavity 14 being moulded or machined into the forward end 10 ofthe plug housing 6 and the raised boss 38 being located within thereceptacle socket 30, a person of ordinary skill in the art wouldunderstand that, with appropriate modifications, the cavity 14 could bemoulded or otherwise formed into the receptacle socket 30 and the bossformed in the forward end 10 of the plug housing 6.

Of note is that the present system can be designed for use as a one waysystem or a two way system. A one way system being defined as a systemwhere keyed connectors can only be connected with a keyed receptacle anda two way system is defined as a system where keyed connectors arebackward compatible with legacy system receptacles (or vice versa),allowing for example, keyed connectors to be used with existingreceptacles.

Referring to FIG. 4, for example, in an illustrative embodiment of a twoway system using existing circular legacy bosses as in 38 ₄ isdisclosed. These legacy bosses 38 ₄ allow for the plug housing 6 of aconnector 2 to be correctly inserted into the socket 30 ₄ regardless ofthe connector keying angle θ (provided, of course, the length X₁ of FIG.2 is less than the length X₂ and corresponds to the radius of the legacyboss 30 ₄).

Referring to FIG. 5A in addition to FIG. 4, an illustrative embodimentof a one way system is disclosed. In order to stop a keyed connector 2from being inserted into a socket such as socket 30 ₄, a tab 39 could bemoulded into or otherwise attached to the outside of the plug housing 6.Referring to FIG. 5B, as known in the art, existing LC type behind thewall (BTW) connectors and receptacles include such an assembly. However,the tabs of these prior art connectors extend only partially along theplug housing 6 and stop at a position Z₁ well short of the forward end10 of the plug housing 6. By extending the tab 39 such that it stops ata position Z₂ closer to the forward end 10 of the plug housing 6, theplug housing 6 can also be prevented from being fully inserted intolegacy LC receptacles. In order for such a connector 2 to be correctlyinserted into a receptacle 26, the socket 30 will have to be modified toinclude a notch within which the tab 39 fits. It will be apparent now toa person of ordinary skill in the art that, in the absence of areceiving groove in the receptacle (all not shown) for the tab 39, or agroove of the correct depth, the tab 39 would butt against thereceptacle housing thereby preventing the user from inserting the plughousing 6 completely into the socket 30.

It is also foreseen that the plug housings 6 and the sockets 30 becolour coded, with a given colour corresponding to a given pair ofkeying angles θ, φ, in order to aid the user in determining whichconnector 2 belongs in which socket 30. Additionally, other coding meanssuch as symbols, alphanumeric characters, etc., may be used alone or incombination with colours to provide a variety of means fordistinguishing keyed connectors and receptacle sockets from one another.

Referring now to FIG. 6, a connector 2 inserted into the first socket 30of a duplex receptacle 26 is shown. Referring to FIG. 7 in addition toFIG. 6, and assuming that the keying angles θ, φ are a matched pair, oninsertion the forward end 10 of the plug housing 6 butts against therear wall 36 of the socket 30. At this point the latch 16 is engaged bythe reciprocal locking mechanism 42 thereby holding the plug housing 6securely in the socket 30. Simultaneously, the ferrule 12 containing theoptic fibre is inserted into the ferrule accepting bore 40 and theraised boss 38 is encircled by the cavity 14, with the exposed end 22 ofthe optic fibre 8 being substantially in alignment with reference planeF. Insertion of a second connector (not shown) into a similar socket 46moulded into the rearward side of the receptacle 26 and in back-to-backrelationship with the socket 30 would have the effect bringing theexposed end of the second connector's optic fibre into close contactwith the exposed end 22 of the optic fibre 8, with the optic fibresbeing substantially axially aligned, and thereby allowing lightpropagating in one of the optic fibres to be transferred to the other.Typically (although not necessarily), sockets as in 30, 46 inback-to-back relationship would have the same predefined receptaclekeying geometries to ensure that fibre optic cables having compatibleconnector keying geometries could be interconnected.

The connector 2 can be readily removed from the receptacle 26 bydepressing the latch 16, thereby releasing the reciprocal lockingmechanism 42.

Referring to FIG. 8, a connector 2 in accordance with an alternativeillustrative embodiment of the present invention is disclosed. In thisembodiment the cavity 14 includes two connector keying portions 24, 24′corresponding to two different connector keying angles θ, θ′. In thismanner, connectors 2 can be provided which mate with the sockets havingreceptacle keying portions with different keying angles φ, provided, ofcourse, that the receptacle keying angle φ matches with one of theconnector keying angles θ, θ′. It will now be apparent to a person ofordinary skill in the art that the number of connector keying portions24 at a variety of keying angles θ could be increased to provided for avariety of keying situations.

Referring to FIG. 9 in addition to FIG. 8, receptacles 26 having sockets30 ₁, 30 ₂, 30 ₃ with raised bosses 38 ₁, 38 ₂, 38 ₃ are disclosed.Raised bosses 38 ₂, 38 ₃ are depicted as having multiple receptaclekeying portions (respectively) 46 ₂, 46 ₂″ and 46 ₃′, 46 ₃″, 46 ₃′″.When combined with a corresponding set of connectors 2 having multipleconnector keying portions 24, 24′, etc., this allows for a widevariation in the number of potential keys which can be used in a givenimplementation.

Referring now to FIG. 10, a connector 2 in accordance with a secondalternative embodiment is disclosed including a plug housing 6 having acavity 48 therein, with the cavity 48 machined or moulded to comprise agenerally circular section 50 and a protuberance 52 such as a ridge, tabor the like running axially along the inside of the cavity 48. Similarto the keying system as discussed hereinabove, the protuberance 52 ispositioned along the inside of the cavity at the requisite keying angle.theta. Referring now to FIG. 11 in addition to FIG. 10, a receptacle 26comprised of one or more sockets 30 having raised bosses 54 is shown.The raised bosses 54 are moulded or machined to include an indentation56, for example such as a notch, slot or flute, therein. Similar to theridge 52, the indentation 56 is positioned on the raised boss 54 at arequisite keying angle φ.

It should be understood that although the protuberance 52 andcorresponding indentation 56 have been portrayed as being symmetricallyconcave in cross section, other shapes of cross sections, for example asquare or triangular notch, could also be applied in the context of thepresent invention. Additionally, the shapes could be asymmetric.

Referring now to FIG. 12 in addition to FIG. 11, in order to prevent astandard connector cable (not shown) from being inserted into a socket30 keyed by a raised boss 54 having an indentation 56 therein, tabs 57can be moulded or otherwise bonded to the inside of the sockets 30 ₁, 30₂, in the receptacle 26. In order for a connector to be inserted into agiven socket 30 ₁, 30 ₂, it will be necessary that the connector plughousing (not shown) be modified to include a suitable notch therein forreception of the tab 57.

Referring to FIG. 13, a connector 2 in accordance with a thirdalternative illustrative embodiment of the present invention isdisclosed. In this embodiment the plug housing 6 is machined or mouldedto include a cavity 58 therein having both an indentation 60 and aprotuberance 62 therein. The indentation 60 and a protuberance 62 arepositioned within the cavity 58 at requisite keying angles as discussedhereinabove. Such a connector 2 would mate with a receptacle having asocket therein with a raised boss including both an indentation and aprotuberance located at keying angles (all not shown) matching thekeying angles of the indentation 60 and the protuberance 62 of theconnector 2.

Referring to FIG. 14, a connector 2 in accordance with a forthalternative illustrative embodiment of the present invention isdisclosed. In this embodiment the plug housing 6 is machined or mouldedto include a cavity 64 having a cross section which varies depending onthe depth of the cavity 64. Illustratively, the cavity 64 is comprisedof an inner aligning portion 66, illustratively cylindrical, and anouter portion 68 having an illustratively oval or egg shaped crosssection with a depth Z and a keying portion 70. In line with the keyedconnectors as already disclosed hereinabove, the keying portion 70 ispositioned at a predetermined keying angle θ from the horizontal axis C.

Referring to FIG. 15 in addition to FIG. 14, the correspondingreceptacle 26 is comprised of one or more sockets 30 having a raisedboss 72 machined, moulded or other wise formed into a rear wall 36thereof. The raised boss 72 is comprised of a lower portion 74 having anillustratively oval or egg shaped cross section and an upper aligningportion 76, illustratively cylindrical. Additionally, the lower portion74 has a protruding keying portion 78 which is positioned at apredetermined keying angle φ from the horizontal axis E. As will now beapparent to a person of ordinary skill in the art, provided the keyingangles θ, φ match, in order for the connector 2 to be insertedcompletely into the receptacle socket 30, the thickness Z of the lowerportion 74 of the raised boss 72 must be the same or less than the depthZ of the upper portion 66 of the cavity 64.

Still referring to FIGS. 14 and 15, provided the keying angles θ, φ.match and the thickness Z is the same as or less than the depth Z, whenthe plug housing 6 is inserted into the socket 30 of the receptacle 26,the cavity 64 will mate with the raised boss 72, thereby allowing theconnector 2 to be securely fastened to the receptacle. If the keyingangles θ, φ do not match, then illustratively the forward end 10 of theplug housing 6 will butt against the protruding keying portion 78 of theraised boss 72 thereby preventing correct insertion of the plug housing6 in the socket 30. Similarly, if the thickness z is somewhat greaterthan the depth z then plug housing 6 will be prevented from beingcompletely inserted into the socket 30, thereby preventing the flexiblelocking tab or latch 16 from being engaged.

Referring now to FIGS. 16, 17 and 18, a receptacle 26 in accordance witha fifth alternative embodiment of the present invention will bedisclosed. The receptacle 26 is similar as to described hereinabove withthe difference that the receptacle keying portion 46 of the raised bossincludes a bevelled or chamfered outer surface 80 in order to facilitateinsertion of a connector (not shown) into the socket 30. Other types ofsurfaces, for example rounded, could also be implemented in order tofacilitate insertion of a connector.

It is also foreseen that the present keying system be field configurableby the installer in order to provide connectors and receptacles with aninstaller selected keying. Referring to FIG. 19A, for example, thecavity 14 would be provided in an interchangeable module 82 forinsertion into a suitably adapted receiving cut out 84 in the forwardend 10 of the plug housing 6. The module 82 would be held in placewithin the plug housing by clips, an adhesive or other suitable securingmeans.

Referring to FIG. 19B, alternatively the raised bosses 38 could bemanufactured separately from the receptacle 26 and including a shaft 86having a second geometry, for example a regular geometric form, such asa triangle, square, hexagon, octagon or the like, a series of grooves 88therein. The shaft 86 would be rotated to the requisite receptaclekeying angle and inserted in a shaft receiving opening 90 having a firstgeometry in the rear wall 36 of each socket 30 until the raised boss isin contact with the rear wall 36. The shaft receiving opening 90 couldinclude, for example, a ridged inner surface 92 adapted to mate with theseries of grooves 88 on the shaft 86. The shaft 86 could also be held inplace within the shaft receiving opening 90 by an adhesive, for example.

Alternatively, the cavities and raised bosses of the invention could bemodifiable and adaptable through removal from or addition to thecavities or raised bosses through the provision of a suitable tool (forexample by cutting away a portion of a raised boss or fluting the insideof a cavity).

Referring to FIG. 20, although the above invention has been describedusing BTW receptacles for interconnecting two connectors, the keyingsystem could also be moulded into single sided receptacles 94 formounting on active components, attenuators and the like (not shown).

Although the present invention has been described hereinabove by way ofan illustrative embodiment thereof, this embodiment can be modified atwill without departing from the spirit and nature of the subjectinvention.

1. A connector system comprising: a set of optical plugs, each opticalplug having a housing and a ferrule, the housing having a front and backorientation and a forward end defining a cavity, the ferrule beingdisposed within the cavity, the housing defining a first keying geometryon the forward end around the cavity, the first keying geometry for eachoptical plug of the set of optical plugs being different; and a set ofoptical receptacles, each optical receptacle having an opening toreceive the optical plug and a ferrule receiving portion to receive theferrule, the ferrule receiving portion defining a second keying geometryto cooperate with the first keying geometry, the second keying geometryfor each optical receptacle of the set of optical receptacles beingdifferent and being adapted to cooperate with one and only one of thefirst keying geometries, wherein plugs and receptacles having keyinggeometries that cooperate are mating pairs; wherein each plug andreceptacle of a mating pair is marked with a matching visualidentification different from plugs and receptacles having differentfirst and second keying geometries, the visual identification being atleast one of colour, alphanumerical indicia and symbols.
 2. Theconnector system of claim 1, wherein the first and second keyinggeometries are one or more protuberances and one or more indentationsfor receiving for receiving the protuberances.
 3. The connector systemof claim 1, wherein the first keying geometry is a combination of atleast one indentation from a plurality of indentation positions, and thesecond keying geometry is a combination of at least one protuberancefrom a plurality of possible protuberance positions.
 4. The connectorsystem of claim 3, wherein the indentation is contiguous with the cavityand runs from the forward end backward.
 5. The connector system of claim4, wherein the indentation is square-shaped in cross-section.
 6. Theconnector system of claim 1, wherein the housing is an LC housing. 7.The connector system of claim 1, wherein the first keying geometry doesnot intrude into the cavity.